Developing device having a porous plate

Abstract

A developing device which includes a housing including an opening toward a photosensitive drum, the housing containing a single-component toner, a developing roller disposed in the opening facing the photosensitive drum so as to transfer the toner to an image-forming area between the developing roller and the photosensitive drum, a porous plate disposed in the opening and kept in contact with the part of the developing roller which is positioned in the housing, the porous plate having pores of such a size so as to allow the toner to pass through, and a toner supply means for supplying the toner from the housing to the porous plate.

What is claimed is: 
     
       1. A developing device comprising a housing including an opening toward a photosensitive drum, the housing containing a single-component toner, a developing roller disposed in the opening facing the photosensitive drum so as to transfer the toner to an image-forming area on the surface of the photosensitive drum, a porous plate disposed in the opening and kept in contact with the part of the developing roller positioned in the housing, the porous plate having pores of such a size as to allow the toner to pass through and a toner supply means for supplying the toner from the housing to the porous plate, the supply means including a roller. 
     
     
       2. A developing device according to claim 1, further comprising a first means for charging the toner with a desired polarity, and a second means for generating an electric field between the toner supply means and the developing roller whereby the charged toner is electromagnetically attracted to the developing roller. 
     
     
       3. A developing device according to claim 1, wherein the porous plate comprises a fixing means whereby the porous plate is fixed to the housing, the fixing means comprising means for equalizing the pressure acting on the developing roller. 
     
     
       4. A developing device according to claim 1, wherein the porous plate is not shorter than the axial length of the developing roller so that the porous plate is kept in contact with the full axial length of the developing roller. 
     
     
       5. A developing device according to claim 1, wherein the developing roller has an equal diameter at each end and has a smaller diameter in a central portion than that at the end. 
     
     
       6. A developing device according to claim 1, wherein the porous plate is provided with means for adjusting the pressure of the porous plate to the developing roller, the pressure adjusting means comprising means for adjusting the position of the porous plate with respect to the housing. 
     
     
       7. A developing device according to claim 1, wherein the porous plate has a shorter length than the axial length of the developing roller and the opposite edges of the porous plate are covered with strips on the sides where the porous plate is kept in contact with the developing roller. 
     
     
       8. A developing device according to claim 1, wherein the porous plate is provided with means for keeping the porous plate in contact with the developing device under an appropriate pressure applied along the axial length of the developing roller. 
     
     
       9. A developing device comprising a housing having an opening and containing a single-component toner, a photosensitive drum, a developing roller positioned to transfer the toner from the housing to an image-forming area on the surface of the photosensitive drum, a porous plate disposed in the opening and in contact with the developing roller, the porous plate having pores of such a size as to allow the toner to pass through, and a toner collecting means for collecting toner through the porous plate, wherein the toner collecting means comprises a window disposed on the porous plate, and having a larger opening than the pores of the porous plate. 
     
     
       10. A developing device comprising a housing having an opening and containing a single-component toner, a photosensitive drum, a developing roller positioned to transfer the toner from the housing to an image-forming area on the surface of the photosensitive drum, a porous plate disposed in the opening and in contact with the developing roller, the porous plate having pores of such a size as to allow the toner to pass through, and a toner collecting means for collecting toner through the porous plate, wherein the toner collecting means is an electrode having an opposite polarity to that of the toner so as to attract the toner, 
     
     
       11. A developing device comprising a housing having an opening and containing a single-component toner, a photosensitive drum, a developing roller positioned to transfer the toner from the housing to an image-forming area on the surface of the photosensitive drum, a porous plate disposed in the opening and in contact with the developing roller, the porous plate having pores of such a size as to allow the toner to pass through, and a toner collecting means for collecting toner through the porous plate, wherein the toner collecting means is a vibrator for imparting vibration to the porous plate.